You can run make symbols and you'll get a debug sandbot.so (or at least it still has symbols in it).
But the stack-strace looks like a problem with Steam - when does it happen? It looks like something is spawning a process (the clone at the top) and I guess either the parent or child process is crashing for some reason.

It's been a little while but I'm still working on it.
The other day someone reported that savegames in single player are blank and I'm working on a fix for that.
I also want to get Opposing Force Capture Point mode working but haven't had a whole lot of time to take a close look at that.